I have aquired a new church account that will require extensive weed control in the cemetary. My question is what kind of post-emergence spray would work best without staining the tombstones. Some of the headstones in the cemetary are the flat ones that seem to have a bronze plaque mounted into the marble. Any suggestions and comments would be welcome. I usually spray with Trimec. Also if a pre-emergent would be more suitable, let me know. Thanks.